System and method for reduced pressure charging

ABSTRACT

A reduced pressure treatment system includes a compressible chamber positionable beneath a foot of a user and being movable between an expanded position and a compressed position. The compressible chamber includes an inlet and an outlet. An inlet valve is in fluid communication with the inlet to prevent fluid within the compressible chamber from exiting the inlet, and an outlet valve is in fluid communication with the outlet to prevent fluid from entering the compressible chamber through the outlet. A biasing member is disposed within the compressible chamber to bias the compressible chamber toward the expanded position, and a manifold is positionable at a tissue site and in fluid communication with the inlet of the compressible chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional applicationSer. No. 12/403,911 filed Mar. 13, 2009 which claims the benefit of U.S.Provisional Application No. 61/036,391 filed Mar. 13, 2008, which ishereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present application relates generally to tissue treatment systemsand in particular to a system and method for reduced pressure charging.

2. Description of Related Art

Clinical studies and practice have shown that providing a reducedpressure in proximity to a tissue site augments and accelerates thegrowth of new tissue at the tissue site. The applications of thisphenomenon are numerous, but application of reduced pressure has beenparticularly successful in treating wounds. This treatment (frequentlyreferred to in the medical community as “negative pressure woundtherapy,” “reduced pressure therapy,” or “vacuum therapy”) provides anumber of benefits, including faster healing and increased formulationof granulation tissue. Typically, reduced pressure is applied to tissuethrough a porous pad or other manifold device. The porous pad containscells or pores that are capable of distributing reduced pressure to thetissue and channeling fluids that are drawn from the tissue. The porouspad often is incorporated into a dressing having other components thatfacilitate treatment.

Reduced pressure treatment systems may include reduced pressure sourcessuch as a powered pump that generates the reduced pressure that isdelivered to a tissue site. However, such reduced pressure sources areoften bulky or obtrusive to a user and are not readily adapted to beused in conjunction with foot treatment systems.

SUMMARY

The problems presented by existing reduced pressure treatment systemsare solved by the systems and methods of the illustrative embodimentsdescribed herein. In one illustrative embodiment, a reduced pressuretreatment system includes a compressible bladder positioned beneath afoot of a user. The compressible bladder includes a chambersubstantially enclosed by a chamber wall, and the compressible bladderis movable between an expanded position and a compressed position togenerate a reduced pressure. A resilient member is operativelyassociated with the chamber wall to bias the compressible bladder towardthe expanded position. A manifold is positioned at a tissue site of theuser and in fluid communication with the chamber of the compressiblebladder.

In another illustrative embodiment, a reduced pressure treatment systemis provided. The reduced pressure treatment system includes acompressible chamber positionable beneath a foot of a user and beingmovable between an expanded position and a compressed position. Thecompressible chamber includes an inlet and an outlet. An inlet valve isin fluid communication with the inlet to prevent fluid within thecompressible chamber from exiting the inlet, and an outlet valve is influid communication with the outlet to prevent fluid from entering thecompressible chamber through the outlet. A biasing member is disposedwithin the compressible chamber to bias the compressible chamber towardthe expanded position, and a manifold is positionable at a tissue siteand in fluid communication with the inlet of the compressible chamber.

In still another illustrative embodiment, a reduced pressure treatmentsystem is provided and includes a compressible bladder positionablebeneath a foot of a user. The compressible bladder includes a chamberand is movable between an expanded position and a compressed position.The system further includes a biasing member disposed within the chamberto bias the compressible bladder toward the expanded position. Apressure regulator having a first variable-volume cavity and a secondvariable-volume cavity is provided. The first variable-volume cavity isfluidly connected to the chamber of the compressible bladder, and amanifold is positionable at a tissue site and in fluid communicationwith the second variable-volume cavity of the pressure regulator.

In yet another illustrative embodiment, a method for providing a reducedpressure to a reduced pressure tissue treatment system used by a user isprovided. The method includes compressing a compressible bladder with afoot of the user and generating the reduced pressure within a chamber ofthe compressible bladder as the compressible bladder expands.

Other objects, features, and advantages of the illustrative embodimentswill become apparent with reference to the drawings and detaileddescription that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic of a reduced pressure treatment systemhaving a compressible bladder system according to an illustrativeembodiment;

FIG. 2 depicts a perspective view of the compressible bladder system ofFIG. 1;

FIG. 3A illustrates a cross-sectional side view of the compressiblebladder system of FIG. 2 taken at 3-3, the bladder system being shown inan expanded position;

FIG. 3B depicts a cross-sectional side view of the compressible bladdersystem of FIG. 2 taken at 3-3, the bladder system being shown in acompressed position;

FIG. 4 illustrates a schematic of a compressible bladder system andpressure regulator according to an illustrative embodiment; and

FIG. 5 depicts an article of orthotic footwear having a compressiblebladder system according to an illustrative embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the following detailed description of several illustrativeembodiments, reference is made to the accompanying drawings that form apart hereof, and in which is shown by way of illustration specificpreferred embodiments in which the invention may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention, and it is understood that otherembodiments may be utilized and that logical structural, mechanical,electrical, and chemical changes may be made without departing from thespirit or scope of the invention. To avoid detail not necessary toenable those skilled in the art to practice the embodiments describedherein, the description may omit certain information known to thoseskilled in the art. The following detailed description is, therefore,not to be taken in a limiting sense, and the scope of the illustrativeembodiments are defined only by the appended claims.

The term “reduced pressure” as used herein generally refers to apressure less than the ambient pressure at a tissue site that is beingsubjected to treatment. In most cases, this reduced pressure will beless than the atmospheric pressure at which the patient is located.Alternatively, the reduced pressure may be less than a hydrostaticpressure associated with tissue at the tissue site. Although the terms“vacuum” and “negative pressure” may be used to describe the pressureapplied to the tissue site, the actual pressure reduction applied to thetissue site may be significantly less than the pressure reductionnormally associated with a complete vacuum. Reduced pressure mayinitially generate fluid flow in the area of the tissue site. As thehydrostatic pressure around the tissue site approaches the desiredreduced pressure, the flow may subside, and the reduced pressure is thenmaintained. Unless otherwise indicated, values of pressure stated hereinare gauge pressures. Similarly, references to increases in reducedpressure typically refer to a decrease in absolute pressure, whiledecreases in reduced pressure typically refer to an increase in absolutepressure.

The term “tissue site” as used herein refers to a wound or defectlocated on or within any tissue, including but not limited to, bonetissue, adipose tissue, muscle tissue, neural tissue, dermal tissue,vascular tissue, connective tissue, cartilage, tendons, or ligaments.The term “tissue site” may further refer to areas of any tissue that arenot necessarily wounded or defective, but are instead areas in which itis desired to add or promote the growth of additional tissue. Forexample, reduced pressure tissue treatment may be used in certain tissueareas to grow additional tissue that may be harvested and transplantedto another tissue location.

Referring to FIG. 1, a reduced pressure treatment system 100 accordingto an illustrative embodiment includes a reduced pressure dressing 104positioned at a tissue site 108 of a patient. The reduced pressuredressing 104 may include a distribution manifold 122 that is positionedadjacent to or in contact with the tissue site 108 to distribute areduced pressure supplied by a reduced pressure source 134. Thedistribution manifold 122 may be any material, either bioabsorbable ornon-bioabsorbable, that is capable of manifolding a reduced pressure tothe tissue site 108. In one embodiment, the distribution manifold 122 isa porous foam and includes a plurality of interconnected cells or poresthat act as flow channels. The porous foam may be a polyurethane,open-cell, reticulated foam such as GranuFoam® dressing manufactured byKinetic Concepts, Inc. of San Antonio, Tex. If an open-cell foam isused, the porosity and pore size may vary, but in one embodiment, thepore size associated with the open-cell foam is about 400 to 600microns. The flow channels allow fluid communication throughout theportion of the distribution manifold 122 having open cells. The cellsand flow channels may be uniform in shape and size, or may includepatterned or random variations in shape and size. Variations in shapeand size of the cells of manifold result in variations in the flowchannels, and such characteristics may be used to alter the flowcharacteristics of fluid through distribution manifold 122.

Distribution manifold 122 may also be constructed from bioresorbablematerials that do not need to be removed from a patient's body followinguse of reduced pressure treatment system 100. Suitable bioresorbablematerials may include, without limitation, a polymeric blend ofpolylactic acid (PLA) and polyglycolic acid (PGA). The polymeric blendmay also include without limitation polycarbonates, polyfumarates,polyhydroxybutarates, polyhydroxyvalerates, polysaccharides,polyaminoacids, and capralactones. Distribution manifold 122 may furtherserve as a scaffold for new cell-growth, or a scaffold material may beused in conjunction with distribution manifold 122 to promotecell-growth. A scaffold is a substance or structure used to enhance orpromote the growth of cells or formation of tissue, such as athree-dimensional porous structure that provides a template for cellgrowth. Illustrative examples of scaffold materials include calciumphosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, orprocessed allograft materials. In one example, the scaffold material hasa high void-fraction (i.e., a high content of air).

The distribution manifold 122 is fluidly connected to the reducedpressure source 134 by a conduit 112. The conduit 112 may fluidlycommunicate with the distribution manifold 122 through a tubing adapter118 positioned adjacent to the distribution manifold 122. A drape 128may be placed over the distribution manifold 122 and sealed around aperimeter of the tissue site 108 to maintain reduced pressure at thetissue site 108.

In the embodiment illustrated in FIG. 1, the reduced pressure source 134is a compressible bladder system 138 that is manually-actuated by a userto provide the reduced pressure to the tissue site. The compressiblebladder system 138 is described in more detail below with reference toFIGS. 2 and 3. Delivery of reduced pressure to the reduced pressuredressing 104 and tissue site 108 encourages new tissue growth bymaintaining drainage of exudate from the tissue site 108, increasingblood flow to tissues surrounding the tissue site 108, and creatingmicrostrain at the tissue site 108.

Referring still to FIG. 1, a canister 142 may be fluidly connectedbetween the reduced pressure source 134 and the tissue site 108 tocollect exudate and other fluids drawn from the tissue site 108. Thecanister 142 includes an inlet that is fluidly connected to the conduit112 and an outlet that is fluidly connected to the reduced pressuresource 134. A liquid-air separator (not shown), such as for example ahydrophobic filter, may be operatively associated with the outlet of thecanister 142 to prevent liquid from exiting the canister 142 through theoutlet. The liquid-air separator prevents the reduced pressure source134 from becoming contaminated by exudate and other biologicallycontaminative materials. As an alternative to the canister 142, or inaddition to the canister 142, the reduced pressure treatment system 100may include additional dressing components at the tissue site 108 thatare capable of storing exudate and other liquids at or near the tissuesite. For example, the reduced pressure dressing 104 positioned at thetissue site 108 may include, in addition to the distribution manifold122, one or more absorbent layers that permit storage of liquid withinthe reduced pressure dressing 104. The liquid storage capabilities ofsuch a dressing may be used in lieu of or in addition to the canister142.

A pressure regulator 148 may be fluidly connected between thecompressible bladder system 138 and the canister 142 to regulate andcontrol the amount of pressure delivered to the canister 142 and thetissue site 108. The pressure regulator may be any device that iscapable of regulating or controlling a reduced pressure or a positivepressure. In one embodiment, the pressure regulator 148 is provided toensure that the reduced pressure delivered to the tissue site 108 doesnot exceed a threshold amount. In other words, the pressure regulatorensures that the absolute pressure supplied to the tissue site 108 isnot too low. A vent (not shown) may be associated with the pressureregulator 148 to raise the absolute pressure within the pressureregulator if more reduced pressure than is needed is provided by thecompressible bladder system 138. The vent may operate by allowingambient air into the pressure regulator when the absolute pressurewithin the pressure regulator 148 drops below a predetermined value.

In addition to the canister 142 and pressure regulator 148, the reducedpressure treatment system 100 may also include sensors, processingunits, alarm indicators, memory, databases, software, display units, anduser interfaces that further facilitate the application of reducedpressure treatment to the tissue site 108. In one example, a sensor (notshown) may be disposed at or near the reduced pressure source 134 todetermine a source pressure generated by the reduced pressure source134. The sensor may communicate with a processing unit that monitors andcontrols the reduced pressure that is delivered by the reduced pressuresource 134.

Referring to FIGS. 2, 3A, and 3B, the compressible bladder system 138includes a pair of compressible bladders 210. Each compressible bladder210 includes a chamber wall 214 that substantially encloses a chamber218. The compressible bladder 210 is movable between an expandedposition (see FIG. 3A) and a compressed position (see FIG. 3B). Abiasing member 224, or resilient member, is disposed within the chamber218 to bias the compressible bladder 210 toward the expanded position.In one embodiment, the biasing member 224 is an open-cell foam such as,for example, a reticulated polyurethane foam similar to that used withthe distribution manifold 122. In another embodiment, the biasing membermay be a spring, sponge, or any other type of resilient material orstructure that is capable of returning the compressible bladder 210 tothe expanded position following compression of the compressible bladder210. In still another embodiment, the biasing member 224 may bepositioned external of the chamber 218 and still have a biasing effectthat urges the compressible bladder 210 toward the expanded position.For example, the biasing member 224 may include a resilient materialthat is bonded, welded, or other attached to or integrated into thechamber wall 214 that causes the chamber wall 214 to resiliently returnto the expanded position. In one embodiment, the biasing member 224 mayinclude the chamber wall 214 without additional structures, components,or materials. More specifically, if the chamber wall 214 is made from asufficiently resilient material, the chamber wall 214 may attempt toreturn the compressible bladder 210 to the expanded position after thecompressive force has been removed.

The chamber 218 of each compressible bladder 210 includes an inlet 230and an outlet 234. An inlet valve 240 is in fluid communication with theinlet 230 to prevent fluid exiting the chamber 218 from passing throughthe inlet 230. An outlet valve 244 is in fluid communication with theoutlet 234 to prevent fluid from entering the chamber 218 through theoutlet 234. The inlet valve 240 and outlet valve 244 may be positionedin conduits fluidly connected to the inlet 230 and outlet 234,respectively, as shown in FIG. 2. Alternatively, the inlet valve 240 andoutlet valve 244 may be more directly associated with or positionedwithin inlet and outlet ports on the compressible bladder 210. The inletvalve 240 and outlet valve 244 may be any particular type of valve forselectively inhibiting or preventing fluid flow, but in one embodiment,the valves 240, 244 are one-way valves such as check valves to allowfluid flow in one direction and prevent fluid flow in another direction.One example of a check valve that may be used with the compressiblebladders 210 is a flapper-type valve that includes a flapper positionedover an aperture in the chamber wall 214. As fluid pressure on one sideof the aperture builds, the flapper moves to an open position to allowfluid communication through the aperture. As fluid pressure on the otherside of the aperture increases, the flapper is moved against theaperture to block fluid communication.

Referring still to FIGS. 2, 3A, and 3B, but also to FIG. 1, in operationthe compressible bladders 210 are positioned beneath a foot 310 of auser. One of the compressible bladders 210 is preferably positionedunder a heel region 314 of the foot 310, and another of the compressiblebladders 210 is preferably positioned under a forefoot region 318 of thefoot 310. As the weight of the user is exerted on a particularcompressible bladder 210, the compressible bladder 210 is compressed tothe compressed position (see FIG. 3B) and gas (e.g. air) that is withinthe chamber 218 is ejected through the outlet 234 and the outlet valve244. The gas that is ejected from the chamber 218 is prevented fromexiting the inlet 230 due to the presence of the inlet valve 240. As theweight of the user is lifted from the compressible bladder 210 that hasbeen compressed, the compressible bladder 210 begins to move toward theexpanded position. The movement of the compressible bladder 210 towardthe expanded position is aided by the biasing member 224. As thecompressible bladder 210 expands, a volume of the chamber 218 increases,which creates a reduced pressure within the chamber 218 relative toambient pressure surrounding the compressible bladder 210. This reducedpressure within the chamber 218 pulls fluid into the chamber 218 throughthe inlet valve 240 and the inlet 230. Fluid is prevented from enteringthe chamber 218 through the outlet 234 due to the presence of the outletvalve 244. The reduced pressure generated by the compressible bladder210 during expansion may be transmitted to the distribution manifold 122by fluidly connecting the manifold 122 to the inlet 230 of thecompressible bladder 210.

The positioning of the compressible bladders 210 under the heel region314 and forefoot region 318 of the foot 310 allows a more consistentapplication of reduced, pressure as the user cyclically applies weightto the heel region 314 and then to the forefoot region 318. Such aregimen of weight distribution is consistent with normal walking orrunning activities, and the compressible bladder system 138 isparticularly suited for generating reduced pressure while a user iswalking or running. As the user distributes weight to the heel region314, the compressible bladder 210 under the heel region 314 compressesto the compressed position. As the user's weight shifts to the forefootregion 318, the compressible bladder 210 under the forefoot region 318compresses to the compressed position. The shifting of weight to theforefoot region 318 relieves the compressive force on the compressiblebladder 210 near the heel region 314, thereby allowing the compressiblebladder 210 under the heel region to expand and generate reducedpressure. When the user's weight shifts back to the heel region 314, thecompressible bladder 210 under the forefoot region 318 expands, therebygenerating reduced pressure. This cycle continues as the user continueswalking, which permits a generation of reduced pressure.

Referring to FIG. 4, a compressible bladder system 408 similar tocompressible bladder system 138 is illustrated. The compressible bladdersystem 138 includes a pair of compressible bladders 410. Eachcompressible bladder 410 includes a chamber wall 414 that substantiallyencloses a chamber 418. The compressible bladder 410 is movable betweenan expanded position and a compressed position similar to thosepreviously described with reference to FIGS. 3A and 3B. A biasingmember, or resilient member, (not shown) is disposed within the chamber418 to bias the compressible bladder 410 toward the expanded position.The biasing member is similar in structure and function to the biasingmember 224 previously described.

The chamber 418 of each compressible bladder 410 includes an inlet 430and an outlet 434. An inlet valve 440 is in fluid communication with theinlet 430 to prevent fluid exiting the chamber 418 from passing throughthe inlet 430. An outlet valve 444 is in fluid communication with theoutlet 434 to prevent fluid from entering the chamber 418 through theoutlet 434. The inlet valve 440 and outlet valve 444 may be positionedin conduits fluidly connected to the inlet 430 and outlet 434,respectively, as shown in FIG. 4. Alternatively, the inlet valve 440 andoutlet valve 444 may be more directly associated with or positionedwithin inlet and outlet ports on the compressible bladder 410. The inletvalve 440 and outlet valve 444 are similar in structure and function tothe valves previously described herein.

In the embodiment illustrated in FIG. 4, the compressible bladder system408 includes a pressure regulator 460 having a first variable-volumecavity 464 and a second variable-volume cavity 468. In one embodiment,the cavities 464, 468 share a common piston wall 472 that is movablebetween a retracted position (not shown) and an extended position (seeFIG. 4) to vary the volume associated with the cavities 464, 468. Thecavities 464, 468 are fluidly separated from each other by a divider476. In one illustrative embodiment, the divider 476 may be a bellowsthat is formed from a sufficiently resilient material.

Each of the cavities 464, 468 includes an outlet (not shown) and aone-way valve (not shown) so that air or other gases within the cavities464, 468 may be expelled from the cavities 464, 468 when the piston wall472 is moved to a retracted position. A user may place the piston wall472 in the retracted position by exerting a compressive force on thepiston wall.

The outlet 434 of each compressible bladder 410 is fluidly connected tothe first variable-volume cavity 464. When the piston wall 472 has beenpositioned in the retracted position, the positively pressured gas fromthe outlet 434 may bias the piston wall 472 toward the extended position(see FIG. 4). As the piston wall 472 moves toward the extended position,the volume of the second variable-volume cavity 468 increases, whichgenerates a reduced pressure within the second variable-volume cavity468. The reduced pressure generated by the compressible bladders 410 andpressure regulator 460 during expansion of the second variable-volumecavity 468 may be transmitted to the distribution manifold 122 byfluidly connecting the manifold 122 to the second variable-volume cavity468 of the pressure regulator 460.

Referring to FIG. 5, a reduced pressure treatment system 500 accordingto an illustrative embodiment includes an article of footwear 508 havinga compressible bladder system 512 which may be similar to any of thecompressible bladder systems described herein. In one embodiment, thecompressible bladder system 512 is fluidly connected to a pressureregulator 516 and a canister 520. The canister 520 may be fluidlyconnected to a reduced pressure dressing 524 positioned at a tissue site528. The reduced pressure generated by the compressible bladder system512 and/or the pressure regulator 516 is delivered to the tissue site528 through the reduced pressure dressing 524, which preferably includesa distribution manifold (not shown). While the tissue site 528 has beenillustrated on a side of a foot stabilized within the article offootwear 508, the tissue site 528 may instead be located in the plantarregion of the foot or on any other region of the foot or lowerextremities. Alternatively, the tissue site 528 may be located on otherparts of the body.

The article of footwear 508 may be an offloading boat, cast walker,neuropathic walker, or any other type of orthotic or therapeuticfootwear. The article of footwear 508 is particularly well suited, whenequipped with the compressible bladder system 512 to treat diabetic footulcers and other foot-related injuries and wounds. The article offootwear 508 may be designed to relieve pressure in injured areas of thefoot of a patient, thereby allowing the patient to remain ambulatory. Asthe patient walks, the compressible bladder system 512 is activated aspreviously described to generate reduced pressure. This reduced pressuremay be directed to the injuries or wounds of the patient to improvehealing through reduced pressure treatment.

A method for providing a reduced pressure to a reduced pressure tissuetreatment system used by a user is provided. The method includescompressing a compressible bladder with a foot of the user, andgenerating the reduced pressure within a chamber of the compressiblebladder as the compressible bladder expands. The compressible bladdermay be similar to any of the compressible bladders or compressiblebladder systems described herein. In one embodiment, the method mayfurther include compressing a second compressible bladder with the footof the user and generating a second reduced pressure within a secondchamber of the second compressible bladder as the second compressiblebladder expands. The second reduced pressure may be substantially thesame as the first reduced pressure, or alternatively may be a higher orlower pressure. When two compressible bladders are provided, the firstcompressible bladder is positioned under a forefoot region of the footand is compressed when the user places weight on the forefoot region.The second compressible bladder is positioned under a heel region of thefoot and is compressed when the user places weight on the heel region.In this manner, both of the compressible bladders are compressed andexpanded during a single stride of the user while walking.

While the compressible bladders described herein are positionablebeneath a foot of a user, the compressible bladders may instead becompressed by applying a force from another part of the body or someother object. Additionally, while a compressible bladder system havingtwo compressible bladders is illustrated, a single compressible bladdermay be used, or alternatively, multiple compressible bladders in excessof two may be used. In one illustrative embodiment, when multiplecompressible bladders are used, each of the compressible bladders isfluidly independent, and each compressible bladder includes one-wayvalves or devices associated with the inlet and outlet of thecompressible bladder.

The pressure regulators described herein may serve to regulate orcontrol the pressure supplied by the compressible bladder system. Withrespect to pressure regulator 460, the pressure regulator may further beused to provide a reduced pressure to a tissue site when a positivepressure is supplied to the pressure regulator. While the use ofpressure regulators may be preferred in some embodiments, in otherembodiments, a pressure regulator may be omitted. In these embodimentsthat do not include a separate pressure regulator, the compressiblebladder may be configured to be self-regulating based on the sizing,shape, and material used for the compressible bladder and the biasingmember. For example, in one embodiment, as the reduced pressure at thetissue site and in the conduit leading to the tissue site increases, thecompressible bladder continues to supply additional reduced pressure aslong as the resiliency of the biasing member or the chamber wall of thecompressible bladder is able to overcome the tendency of thecompressible bladder to remain collapsed. When the biasing member orchamber wall is no longer able to expand following compression due tothe amount of reduced pressure in the conduit leading to the tissuesite, the compressible bladder will no longer generate additionalreduced pressure.

It should be apparent from the foregoing that an invention havingsignificant advantages has been provided. While the invention is shownin only a few of its forms, it is not just limited but is susceptible tovarious changes and modifications without departing from the spiritthereof.

We claim:
 1. A reduced-pressure source for operation by a foot to supplya reduced pressure to a tissue site, the reduced-pressure sourcecomprising: a compressible bladder adapted to be positioned beneath thefoot, the compressible bladder having a chamber substantially enclosedby a chamber wall and being movable between an expanded position and acompressed position; a biasing member operatively associated with thechamber wall to bias the compressible bladder toward the expandedposition; and a pressure regulator fluidly connected to the chamber andadapted to regulate the reduced pressure delivered to the tissue site,the pressure regulator having a first variable volume cavity fluidlyconnected to the chamber of the compressible bladder.
 2. Thereduced-pressure source of claim 1, wherein the compressible bladder isadapted to generate a reduced pressure within the chamber as thecompressible bladder moves toward the expanded position.
 3. Thereduced-pressure source of claim 1, wherein the biasing member isdisposed within the chamber.
 4. The reduced-pressure source of claim 1,wherein the biasing member is an open-cell foam.
 5. The reduced-pressuresource of claim 1, wherein the biasing member is bonded to the chamberwall.
 6. The reduced-pressure source of claim 1, wherein the biasingmember is welded to the chamber wall.
 7. The reduced-pressure source ofclaim 1, wherein the compressible bladder is a first compressiblebladder, the reduced-pressure source further comprising: a secondcompressible bladder adapted to be positioned beneath the foot, thesecond compressible bladder having a second chamber substantiallyenclosed by a second chamber wall and being movable between an expandedposition and a compressed position; and a second biasing memberoperatively associated with the second chamber wall to bias the secondcompressible bladder toward the expanded position.
 8. Thereduced-pressure source of claim 7, wherein the first compressiblebladder is adapted to be positioned beneath a forefoot region of thefoot and the second compressible bladder is adapted to be positionedbeneath a heel region of the foot.
 9. The reduced-pressure source ofclaim 1, further comprising: an inlet valve in fluid communication withan inlet of the compressible bladder to prevent fluid within the chamberfrom exiting the inlet; and an outlet valve in fluid communication withan outlet of the compressible bladder to prevent fluid from entering thechamber through the outlet.
 10. The reduced-pressure source of claim 1,wherein the compressible bladder is a first compressible bladder, thereduced-pressure source further comprising: a second compressiblebladder adapted to be positioned beneath the foot, the secondcompressible bladder having an inlet, an outlet, and a second chambersubstantially enclosed by a second chamber wall, and being movablebetween an expanded position and a compressed position; a second biasingmember operatively associated with the second amber wall to bias thesecond compressible bladder toward the expanded position; an inlet valvein fluid communication with the inlet of the second compressible bladderto prevent fluid within the second chamber from exiting the inlet; andan outlet valve in fluid communication with the outlet of the secondcompressible bladder to prevent fluid from entering the second chamberthrough the outlet.
 11. The reduced-pressure source of claim 1, wherein:the first variable-volume cavity is configured to expand as the firstvariable-volume cavity receives a positively pressured air from thechamber.
 12. The reduced-pressure source of claim 1, wherein: thepressure regulator has a second variable-volume cavity; and the secondvariable-volume cavity is configured to expand and generate a reducedpressure as the first variable-volume cavity expands.
 13. Thereduced-pressure source of claim 1, wherein: the pressure regulator hasa second variable-volume cavity; the first variable-volume cavity isconfigured to expand as the first variable-volume cavity receives apositively pressured air from the chamber; and the secondvariable-volume cavity is configured to expand and generate a reducedpressure as the first variable-volume cavity expands.
 14. Thereduced-pressure source of claim 1, wherein: the pressure regulator hasa second variable-volume cavity; and the pressure regulator includes abellows device fluidly separating the first variable-volume cavity andthe second variable-volume cavity.
 15. The reduced-pressure source ofclaim 1, further comprising a manifold adapted to be positioned at thetissue site and in fluid communication with the chamber of thecompressible bladder.
 16. The reduced-pressure source of claim 1,further comprising a canister fluidly connected to the chamber.
 17. Thereduced-pressure source of claim 1, further comprising: a manifoldadapted to be positioned at the tissue site and in fluid communicationwith the chamber of the compressible bladder; and a canister fluidlyconnected between the chamber and the manifold.
 18. The reduced-pressuresource of claim 1, wherein the pressure regulator comprises a ventadapted to regulate a flow rate of the reduced pressure that isdelivered to the tissue site by allowing ambient air into the pressureregulator.
 19. A reduced-pressure source for operation by a foot tosupply a reduced pressure to a tissue site, the reduced-pressure sourcecomprising: a first compressible bladder adapted to be positionedbeneath a forefoot region of the foot, the first compressible bladderhaving a first chamber substantially enclosed by a first chamber walland being movable between an expanded position and a compressedposition; a first biasing member operatively associated with the firstchamber wall to bias the first compressible bladder toward the expandedposition; a second compressible bladder adapted to be positioned beneatha heel region of the foot, the second compressible bladder having asecond chamber substantially enclosed by a second chamber wall and beingmovable between an expanded position and a compressed position; and asecond biasing member operatively associated with the second chamberwall to bias the second compressible bladder toward the expandedposition.
 20. The reduced-pressure source of claim 19, wherein the firstcompressible bladder and the second compressible bladder are adapted togenerate a reduced pressure within the first chamber and the secondchamber, respectively, as the first compressible bladder and the secondcompressible bladder move toward the expanded position.
 21. Thereduced-pressure source of claim 19, wherein the first biasing member isdisposed within the first chamber and the second biasing member isdisposed within the second chamber.
 22. The reduced-pressures source ofclaim 19, wherein the first biasing member and the second biasing memberare an open-cell foam.
 23. The reduced-pressure source of claim 19,further comprising: a first inlet valve in fluid communication with aninlet of the first compressible bladder to prevent fluid within thechamber from exiting the inlet; a first outlet valve in fluidcommunication with an outlet of the first compressible bladder toprevent fluid from entering the chamber through the outlet; a secondinlet valve in fluid communication with an inlet of the secondcompressible bladder to prevent fluid within the second chamber fromexiting the inlet of the second compressible bladder; and a secondoutlet valve in fluid communication with an outlet of the secondcompressible bladder to prevent fluid from entering the second chamberthrough the outlet of the second compressible bladder.
 24. Thereduced-pressure source of claim 19, further comprising a pressureregulator fluidly connected to the first chamber and the second chamberand adapted to regulate the reduced pressure delivered to the tissuesite.
 25. The reduced-pressure source of claim 24, wherein the pressureregulator has a variable-volume cavity fluidly connected to the firstchamber and the second chamber.
 26. The reduced-pressure source of claim24, wherein: the pressure regulator has a variable-volume cavity fluidlyconnected to the first chamber and the second chamber; and thevariable-volume cavity is configured to expand as the variable-volumecavity receives a positively pressured air from at least one of thefirst chamber and the second chamber.
 27. The reduced-pressure source ofclaim 24, wherein: the pressure regulator has a first variable-volumecavity and a second variable-volume cavity, the first variable-volumecavity being fluidly connected to the first chamber and the secondchamber; and the second variable-volume cavity is configured to expandand generate a reduced pressure as the first variable-volume cavityexpands.
 28. The reduced-pressure source of claim 24, wherein: thepressure regulator has a first variable-volume cavity and a secondvariable-volume cavity, the first variable-volume cavity being fluidlyconnected to the first chamber and the second chamber; the firstvariable-volume cavity is configured to expand as the firstvariable-volume cavity receives a positively pressured air from at leastone of the first chamber and the second chamber; and the secondvariable-volume cavity is configured to expand and generate a reducedpressure as the first variable-volume cavity expands.
 29. Thereduced-pressure source of claim 24, wherein: the pressure regulator hasa first variable-volume cavity and a second variable-volume cavity, thefirst variable-volume cavity being fluidly connected to the firstchamber and the second chamber of the first compressible bladder and thesecond compressible bladder, respectively; and the pressure regulatorincludes a bellows device fluidly separating the first variable-volumecavity from the second-variable volume cavity.